The jet, which departed from New York, crashed in Guyana early Saturday morning. The plane broke in two just before reaching a 200-foot ravine. It was 1:30 a.m. and dark and rainy outside.

None of the 163 people on board were killed but about 100 people received medical attention for injuries, which included broken legs and scratches.

There appears to have been no fire after the crash, allowing passengers to exit the plane safely. People said they scrambled out through the emergency exit and over the wings.

The U.S.-made Boeing 737-800 overshot the 7,400-foot (2,200-meter) runway at Cheddi Jagan International Airport, crashing through a chain-link airport fence and ending up on a dirt road around the airport.

Local officials have asked the National Transportation Safety Board (NTSB) to assist in the investigation.

"The first thing the flight investigators are going to look at are what we call the flight dynamics, in other words where did they touch down on the runway, how far down, was it too far, how fast were they going and was there water on the runway that would have let them hydroplane on a thin film of water," ABC News aviation consultant John Nance said.

The other key issue officials will look at is whether the pilots forgot to open up the wing flaps, which would have been critical for slowing down the plane on landing.

Investigators will be looking at the issue of pilot fatigue, given the early morning landing.

"No question, when you are looking at accidents on the backside of the clock one of the key questions is was the crew tired, either directly or cumulatively tired over time. These things can be very important in figuring out exactly what happened," Nance added.

Sources in Guyana say they are ruling out weather as a factor in the crash. The plane's black boxes have been recovered, which will help investigators figure out the cause of the crash.

"We are very, very grateful that more people were not injured," said Guyana President Bharrat Jagdeo, who came to the crash site before dawn.

"It was serious and all the plane practically broke in two, so we should be very grateful for that," Jagdeo said.

ABC News' Lisa Stark and The Associated Press contributed to this report.